linux-kernel - [PATCH v3 1/1] x86/init: Noop get/set wallclock when platform doesn't support RTC

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Date:   Thu, 10 Oct 2019 17:28:56 +0800
From:   Rahul Tanwar <rahul.tanwar@...ux.intel.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        tony.luck@...el.com, x86@...nel.org
Cc:     andriy.shevchenko@...el.com, alan@...ux.intel.com,
        linux-kernel@...r.kernel.org, qi-ming.wu@...el.com,
        chuanhua.lei@...ux.intel.com, cheol.yong.kim@...el.com,
        Rahul Tanwar <rahul.tanwar@...ux.intel.com>
Subject: [PATCH v3 1/1] x86/init: Noop get/set wallclock when platform doesn't support RTC

Use wallclock_init() op to detect platforms which does not support RTC and
noop get/set wallclock ops for such platforms.

Suggested-by: Andy Shevchenko <andriy.shevchenko@...el.com>
Signed-off-by: Rahul Tanwar <rahul.tanwar@...ux.intel.com>
---
 arch/x86/kernel/x86_init.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 18a799c8fa28..4f572fd942eb 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -31,6 +31,30 @@ static int __init iommu_init_noop(void) { return 0; }
 static void iommu_shutdown_noop(void) { }
 bool __init bool_x86_init_noop(void) { return false; }
 void x86_op_int_noop(int cpu) { }
+static int set_rtc_noop(const struct timespec64 *now) { return -EINVAL; }
+static void get_rtc_noop(struct timespec64 *now) { }
+
+static const struct of_device_id of_cmos_match[] = {
+	{ .compatible = "motorola,mc146818" },
+	{}
+};
+
+static void x86_wallclock_init(void)
+{
+	struct device_node *node;
+
+	node = of_find_matching_node(NULL, of_cmos_match);
+	if (node && !of_device_is_available(node)) {
+		/*
+		 * Some products do not support RTC as persistent clock source. This can be
+		 * optionally indicated by having status property as disabled in the
+		 * corresponding DT node. Override get/set wallclock routines to noops for
+		 * such products.
+		 */
+		x86_platform.get_wallclock = get_rtc_noop;
+		x86_platform.set_wallclock = set_rtc_noop;
+	}
+}
 
 /*
  * The platform setup functions are preset with the default functions
@@ -73,7 +97,7 @@ struct x86_init_ops x86_init __initdata = {
 	.timers = {
 		.setup_percpu_clockev	= setup_boot_APIC_clock,
 		.timer_init		= hpet_time_init,
-		.wallclock_init		= x86_init_noop,
+		.wallclock_init		= x86_wallclock_init,
 	},
 
 	.iommu = {
-- 
2.11.0